1. Field of the Invention
This invention relates to a transom for boats, and more specifically concerns a transom for pleasure or work boats having outboard motors or inboard/outboard motors.
2. Description of the Prior Art
Many pleasure and work boats today are constructed of synthetic resin plastic material reinforced by fibers. The most common fiber used is glass fibers, such as Fiberglass, and the most common synthetic resin plastic used is a polyester resin.
The fibers may also be Kevlar man-made fibers or carbon fibers, but, because of the cost and complexity in applying these materials, they are used in only a small percentage of fiber-reinforced plastic boats. Kevlar is a registered trademark of E. I. du Pont de Nemours and Company, Wilmington, Del.
The synthetic resin plastic material may also be an epoxy resin, a vinyl ester resin, a urethane/polyester resin, or any other suitable synthetic resin plastic material.
Aluminum is second in popularity to fiber-reinforced synthetic resin plastic as a construction material for the hulls of pleasure boats.
The majority of such boats are powered by outboard motors or inboard/outboard motors. Some also are sailboats, deriving their main propulsion force from the wind, with the outboard motor or inboard/outboard motor providing intermittent propulsion as needed.
Such boats are provided with a transom, which is an upright, transverse portion of the hull that fits across the stern of the boat. The power source of the boats is an outboard motor which is mounted outboard of the transom on an extension bracket or hung directly from the transom, or an inboard/outboard motor which is mounted inboard of the transom with its drive shaft extending through a hole in the transom to a drive unit containing the propeller which drive unit is mounted outboard of the transom. The power source of an inboard/outboard is mounted directly on the transom, but may also be supported by brackets which extend from the hull reinforcing stringers. The power source exerts a considerable force on the transom when the boat is being started, and also when the boat is underway. The transom must be constructed very sturdily to resist the propulsion force of the motor.
Conventionally, the transom comprises a plywood sheet, one-half to one-and-one-half inches thick, sandwiched between outer and inner layers of the basic hull material of fiber-reinforced synthetic resin plastic.
Also conventionally, the hull of a pleasure boat may be constructed of fiber-reinforced synthetic resin plastic in the following way. An outer hull liner is constructed by providing a female mold for the hull outer liner, and coating the mold with a wax or some other release agent. Then a polyester resin containing a coloring agent ("gel coat") is sprayed onto the mold to form a smooth outer layer of approximately 0.020 to 0.030 inches which is then allowed to cure. A layer of polyester resin and glass fibers is placed onto the gel coat layer and allowed to cure. Successive layers of glass fiber reinforced polyester resin are applied to the mold and allowed to cure to build up the thickness of the hull outer liner to a desired thickness. Then a smooth inner layer of polyester resin may be added to conceal the glass fibers from view. The hull is then separated from the mold. Other synthetic resins may be substituted for the polyester resin in this method of making a boat hull.
Again conventionally, the transom is formed by gluing together two sheets of plywood using, for example, a resin, to form a laminated sheet of plywood, and then gluing the laminated plywood sheet to the inside surface of the stern wall of the outer liner of the hull. The laminated plywood sheet is clamped onto the inside surface of the outer liner until the resin sets. The inner plywood surface which is exposed to view from the bow of the boat is then coated manually with layers of polyester resin-saturated glass fibers. Again, other synthetic resins may be used in place of the polyester resin.
The inner surface of the laminated plywood sheet which is exposed to view from the bow may also be covered by a preformed hull inner liner that is mated to the hull outer liner. The hull inner liner is made in a manner similar to the hull outer liner, with successive layers of polyester resin and glass fibers being applied to a mold, except that a male mold is used instead of a female mold.
The conventional inboard/outboard transom includes an opening cut into the transom to accommodate the mounting of the drive unit to the motor, the drive unit being a separate entity from the motor.
In an outboard motor boat, the outboard motor is mounted on the transom so that it hangs outside the boat and no opening in the transom is needed.
With an inboard/outboard motor, the motor is mounted inside the transom and is connected to the drive unit through the cut-out portion of the transom.
One of the major problems of outboard motor boats and inboard/outboard motor boats is that the plywood in the conventional transom tends to rot because the water penetrates into the plywood sheets.
In outboard motor boats, water leaks into the plywood of the transom through poorly sealed joints, or through failed seals for various fittings in the transom such as ski tow rings, hull drain plugs, etc.
In inboard/outboard motor boats, the plywood in the transom rots when water penetrates into the plywood around the opening for the motor to drive unit connection, or through failed seals for various fittings in the transom such as ski tow rings, hull drain plugs, etc.
The rotting of the plywood in the transom is a major problem not only for boat owners, but also for boat manufacturers who must spend large sums to repair or replace damaged transoms on warranty claims resulting from such water damage.
Another major problem of boat manufacturers is the time delay in the production of boats caused by the length of time it takes to make a conventional boat transom. It takes time to allow the adhesives to cure that bind the laminated plywood sheets to the hull. Also, putting the plywood in place by hand, and clamping it to hold it there by hand, involves a substantial amount of time and labor.